ProgramNode(0...8)(
  [],
  StatementsNode(0...8)(
    [InterpolatedStringNode(0...8)(
       (0...1),
       [StringNode(1...3)(nil, (1...3), nil, "a "),
        EmbeddedStatementsNode(3...7)(
          (3...5),
          StatementsNode(5...6)(
            [CallNode(5...6)(nil, nil, (5...6), nil, nil, nil, nil, 0, "b")]
          ),
          (6...7)
        )],
       (7...8)
     )]
  )
)
